This invention relates generally to catheters which are utilized within narrowed vasculature such as at the site of a stenosis. More particularly, the present invention deals with catheters allowing blood perfusion within such narrowed vasculature.
Atherosclerosis, the progressive narrowing and hardening of blood vessels over time, may often result in a disabling blockage or narrowed vessel walls. Traditionally, when the blockage involved coronary vasculature, treatment was by way of a coronary bypass operation. The bypass involves placing the patient under general anesthesia, opening the patient""s chest cavity and surgically grafting a vein or artery from another part of the patient""s body onto the patient""s coronary artery. The bypass operation is very traumatic, difficult and expensive. Recovery time is long and painful with a less than certain outcome. Additionally, relief is often only temporary.
Due to the drawbacks of coronary bypass operations, minimally invasive treatment methods, allowing the blockage to be treated selectively and locally, are becoming more common. This type of surgery will most likely employ a catheter to deliver a host of devices to the site of the blockage. These devices may be balloons, stents, drug or radiation delivery devices or a host of other devices for selectively treating the blocked artery at the site of the blockage. The patient will often experience immediate relief along with a brief, more comfortable and less expensive recover. However, a catheter is generally prone to create an ischemic condition when passing through a narrowed vessel.
To be effective, a cardiac catheter must be placed and utilized with great precision. The catheterization team needs to know measurements including location, size, shape and consistency of the blockage (atheroma) as well as the surrounding arterial structures. Therefore visualization by the use of ultrasound allow for visual monitoring of the treatment being performed. Intravascular ultrasound (IVUS) imaging or other visualization techniques may be performed with an imaging device delivered to the site of interest. Imaging allows the measurements above to be made, thus, making treatment more effective.
The IVUS catheter has a tubular shaft surrounding an inner core. The core is rotatable, and usually longitudinally translatable, within the shaft. The shaft prevents the rotating core from damaging vasculature when inserted thereinto. Conventional practice is to first locate the stenosis site by angiography (i.e. injection of contrast material into a blood vessel for external imaging purposes). The stenosis is then traversed with a guidewire. The guidewire may be inserted into the patient""s femoral artery through a small puncture wound in the patient""s upper thigh. The IVUS catheter is then inserted over the guidewire. The IVUS catheter is positioned to allow intravascular ultrasound measurement and imaging of the artery, a distal and proximal reference segment thereof and the entire length of the stenotic region. The core is preferably translated longitudinally as far distal as practicable during IVUS catheter insertion in order to support the shaft, especially at a thin imaging zone at the distal portion of the shaft.
The distal end of the core includes an ultrasonic transducer. The transducer emits short pulses of ultrasound toward the wall of the artery. As the ultrasound enters the blockage and passes through surrounding tissue, the structures within the blockage, and various layers thereof, echoes are returned. An image is built by directing pulses at different parts of the artery. The pulses are directed by rotating the core and thus the transducer. With each rotation, a cross-section is assembled into a fairly detailed two-dimensional picture of the artery as viewed from the inside thereof. The shaft, which is relatively transparent to the ultrasound, prevents the shaft from scraping or battering the artery wall.
Once inserted to a position adjacent the stenosis, the preferred practice is to start imaging with the core advanced to a distal most position within the shaft. Images are recorded as the core is moved (i.e. longitudinally translated) proximally, within the stationary shaft, until the entire artery has been imaged. This practice is known as a pullback. This provides a complete record of the stenosis site and the vasculature used to access the stenosis. The IVUS catheter is then removed and the recorded images examined and measured, as directed by the physician
The shaft is often large enough to completely block the artery (i.e. ischemia) when placed across the stenosis. As a result, the patient will often experience increasing pain and distress when the IVUS shaft is introduced into the target area. In response to the ischemia the physician will often withdraw the shaft far enough proximal to the blockage to restore blood flow. Before imaging can continue, time is lost as the heart muscle recovers sufficiently to withstand another possible ischemic episode.
The inefficiency which results from the shaft induced ischemia is better understood when considering that an effective pullback may need to last as long as 100 to 200 seconds. This does not count the time necessary for catheter placement and any preliminary imaging the physician may wish to perform. While the amount of effective time required during the procedure may be somewhat limited as noted above, the actual time necessary to accomplish the procedure is greatly affected by the number of ischemic episodes which result. Furthermore, the effective time is long enough such that once an ischemic condition is caused at the target are, it is likely to reappear several times before the procedure is completed. Not only does this affect the procedure but it affects the patient as well. That is, withdrawing and reinserting the shaft through the stenosis can injure the artery and may dislodge material from the stenosis. An injured artery or disrupted stenosis is more likely to form blood clots or another stenosis. Similar occlusion problems can result with other catheter devices as well. Therefore, what is desired is a perfusion catheter having features to enhance perfusion during an intravascular procedure.
In an embodiment of the invention a perfusion catheter is provided with a shaft having a lumen and a plurality of ports through the shaft. A rotatable core having a core groove is disposed within the lumen.
In a method of the invention circulation in a vessel is allowed for while a catheter shaft housing a retractable core and having a plurality of ports is placed across the vessel. The retractable core is retracted to expose a portion of the plurality of ports and allow a flow of blood into a shaft lumen of the catheter shaft.
In an alternate method of the invention circulation in a vessel is maintained during a catheterization procedure. A catheter shaft having a plurality of ports is guided to the vessel. A core having a core groove is rotated within a lumen of the shaft.